//生成id
const uuid = (len, radix) => {
    var chars = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz'.split('');
    var uuid2 = [],
        i;
    radix = radix || chars.length;
    if (len) {
        // Compact form
        for (i = 0; i < len; i++) uuid2[i] = chars[0 | Math.random() * radix];
    } else {
        // rfc4122, version 4 form
        var r;
        // rfc4122 requires these characters
        uuid2[8] = uuid2[13] = uuid2[18] = uuid2[23] = '-';
        uuid2[14] = '4';
        // Fill in random data.  At i==19 set the high bits of clock sequence as
        // per rfc4122, sec. 4.1.5
        for (i = 0; i < 36; i++) {
            if (!uuid2[i]) {
                r = 0 | Math.random() * 16;
                uuid2[i] = chars[(i == 19) ? (r & 0x3) | 0x8 : r];
            }
        }
    }
    return uuid2.join('');
}

module.exports = uuid;